[Sync] Remove DropAttachments from AttachmentService and SyncData

sync/api/sync_data.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sync/api/sync_data.h"
 
 #include <ostream>
 
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 200 matching lines @@
 int64 SyncDataRemote::GetId() const {
   return id_;
 }
 
 void SyncDataRemote::GetOrDownloadAttachments(
     const AttachmentIdList& attachment_ids,
     const AttachmentService::GetOrDownloadCallback& callback) {
   attachment_service_.GetOrDownloadAttachments(attachment_ids, callback);
 }
 
-void SyncDataRemote::DropAttachments(
-    const AttachmentIdList& attachment_ids,
-    const AttachmentService::DropCallback& callback) {
-  attachment_service_.DropAttachments(attachment_ids, callback);
-}
-
 }  // namespace syncer